Fortinet IPS Configuring SYN flood protection, Configure the options for tcpsynflood Select OK

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Configuring SYN flood protection

SYN flood attacks

Configuring SYN flood protection

To configure the SYN flood protection

1Go to Intrusion Protection > DoS Sensor.

2Select Create New.

3Configure the options for tcp_syn_flood.

4Select OK.

Figure 18: Configuring the syn_flood anomaly

Suggested settings for different network conditions

The main setting that impacts the efficiency of the pseudo SYN proxy in detecting SYN floods is the threshold value. The default threshold is 2000. Select an appropriate value based on network conditions. Normally, if the servers being protected by the FortiGate unit need to handle heavier requests, such as a busy web server, the threshold should be set to a higher value. If the network carries lighter traffic, the threshold should be set to a lower value.

	FortiGate IPS User Guide Version 3.0 MR7
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Contents E R G U I D E Trademarks Contents DoS sensors Protocol decodersIPS sensors SYN flood attacksIntroduction FortiGate IPSDocument conventions About this documentFortinet documentation Typographic conventionsFortiGate Pptp VPN User Guide Customer service and technical support Fortinet Knowledge CenterComments on Fortinet technical documentation IPS overview and general configuration IPS settings and controlsThis section contains the following topics Default fail open setting When to use IPSDefault signature and anomaly settings Config ips global Set fail-open enable disable endMonitoring the network and dealing with attacks Setting the buffer sizeConfiguring logging and alert email Controlling sessionsAttack log messages Signature Anomaly FortiGuard CenterAdding protection profiles to firewall policies Using IPS sensors in a protection profileCreating a protection profile that uses IPS sensors Select Create NewAdding protection profiles to user groups Using IPS sensors in a protection profile Predefined signatures IPS predefined signaturesViewing the predefined signature list Column SettingsEnable Clear All FiltersCreate a sensor and add IPS filters to it Viewing the predefined signature list Custom signatures IPS custom signaturesViewing the custom signature list Adding custom signatures using the CLI Custom signature configurationAdding custom signatures using the web-based manager Command syntax patternCreating custom signatures Custom signature fieldsShows the valid characters for custom signature fields Name BufferOverflow Custom signature syntaxAttackid SrcportContent keywords Keyword and value Description Deprecated, see pattern and context keywords Pattern yahoo.com Pattern GETContext uri Context hostRegexdelimismxAEGRU PcreRegex/mdelim Uri !uristrProtocol tcp IP header keywords Keyword and Value DescriptionTCP header keywords Keyword and Value Description Tcpflags AP Tcpflags S,12UDP header keywords Keyword and Value Description Icmp keywords Keyword and Value UsageOther keywords Keyword and Value Description Example 1 signature to block access to example.com Example custom signaturesSbid --name Block.example.com Sbid --name Block.example.com Example 2 signature to block the Smtp ‘vrfy’ command Sbid --name Block.SMTP.VRFY.CMDSbid --name Block.SMTP.VRFY.CMD --pattern vrfy Creating custom signatures Protocol decoders Protocol decodersUpgrading the IPS protocol decoder list Viewing the protocol decoder list Protocol decoder list Protocols Protocol decoder names PortIPS sensors AlldefaultAlldefaultpass Viewing the IPS sensor listProtectclient Configuring IPS sensorsAdding an IPS sensor ProtectemailserverIPS sensor attributes IPS sensor filtersIPS sensor overrides Configuring filtersReset Delete and Edit Delete or edit the filter IconsConfiguring pre-defined and custom overrides ApplicationExempt IP SourceDoS sensors Sequence in which the sensors examine network traffic Configuring DoS sensorsViewing the DoS sensor list Appears, and select OKName Enter or change the DoS sensor name Comments Anomaly configurationDoS sensor attributes Will appear in the DoS sensor listUnderstanding the anomalies Udpscan Anomaly Description TcpdstsessionUdpflood UdpsrcsessionUnderstanding the anomalies What is a SYN flood attack? SYN flood attacksHow SYN floods work FortiGate IPS Response to SYN flood attacks What is SYN threshold?What is SYN proxy? How IPS works to prevent SYN floodsIPS operation before synflood threshold is reached Configuring SYN flood protection Suggested settings for different network conditionsConfigure the options for tcpsynflood Select OK How Icmp sweep attacks work What is an Icmp sweep?Icmp sweep attacks FortiGate IPS response to Icmp sweep attacksPredefined Icmp signatures Icmp sweep anomalies Configuring Icmp sweep protection Index FortiGate Version 3.0 MR7 IPS User GuideTechnical support